This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. This project's goal is to develop an understanding of the cellular and molecular mechanisms of cytomegalovirus (CMV) persistence in the host. HCMV is a species-specific virus that establishes a persistent/latent infection in the host after primary infection. This ability requires avoidance of immune detection and limitation of cytopathic effect on cells harboring virus. Herpesviruses achieved this by restricting expression of the majority of the viral genome, thereby reducing acute replication and minimizing the potential for presentation of antigenic proteins, while maintaining the ability to reactivate at a later stage. The process by which herpesviruses restrict their own gene expression, thereby promoting a persistent or latent state, is not well understood, but is likely to involve both cellular and viral factors. The recent discovery of RNA interference and the widespread expression of microRNAs has uncovered a new layer of post-transcriptional gene regulation. Studies have suggested that a large percentage of transcripts may be targeted and regulated by miRNAs, thus regulation by small RNAs may represent a crucial mechanism in the control of gene expression. This project will extend the characterization of HCMV UL112-1 during acute and persistent infection;identify and characterize the HCMV gene targets of other virally encoded miRNAs;analyze the miRNAs contribution to regulation of the virus during acute infection;and examine the expression and function of the HCMV miRNAs in monocyte macrophages and persistently infected endothelial cells. Elucidating the mechanisms of miRNA regulation of HCMV gene expression will provide an important contribution to the herpesviruses and miRNA field.